Lubricant for cold drawing of thorium wire



United States Patent LUBRICANT FOR COLD DRAWING 0F THORIUM WIRE Charles D. Graham, Jr., Birmingham, England, and Raymond J. Donley, Elyria, Ohio, 'assi'gn'or's to the United States of America as represented by the United States Atomic Energy Commission.

No Drawing. Application March :16, 1954,

Serial N0. 416,721

4 Claims. (01.252 25 The present invention is concerned with a novel lubricant for cold working metals and particularly with a lubrig ant for drawing or extruding such relatively soft metals as thorium and zirconium.

drawing can be accomplished fairly easily, there are other groups of metals which, although soft, are very diflicult to draw because the soft, gummy metals tend to gall or seize in the die. Thorium, titanium, uranium and zirconium are metals of this group.

It has been found that conventional die lubricants are ineffective in preventing galling in the drawing of such metals through metal dies. In tests on the drawing of thorium wire through metal dies of the tungsten carbide type, many different natural and artificially produced lubricants were tried. These included such natural waxes as parafiin, beeswax, carnauba wax, and various commercially produced waxes. Greases such as petroleum jelly, vacuum stopcock grease and stopcock grease containing silicone were also tried unsuccessfully. Other miscellaneous lubricants which were found to be unsatisfactory included molybdenum disulfide, alone or in combination with natural waxes, colloidal graphite, alone and suspended in oil, water or wax, copper suspended in many different vehicles, various soaps, both alone and in combination with lime, and various waxes and fumed lead and zinc oxides'in various suspending agents. In all cases in which the thorium rod was coated with these various lubricants the rod would gall or seize in the die as soon as pressure was applied or at least within one or two inches.

it is an object of the present invention to provide a. novel lubricant useful in the drawing of soft metals.

It is an additional object of the present invention to provide a lubricant useful in the drawing of thorium.

Other objects will be apparent from the description which follows. 1

It has been found in accordance with the present invention that a mixture of molybdenum disulfide and fumed lead and zinc oxides, suspended in a drying medium, is a suitable lubricant for drawing metals and particularly such soft, gummy metals as uranium, thorium, zirconium and titanium. This lubricant maybe used in the conventional manner and will permit the drawing of the soft metals through metal dies of the tungsten carbide type without seizing or galling even when a reduction as great as 21% is effected by the drawing pass.

The solid components of the present composition are combined together in a ratio of molybdenum disulfide to fumed lead-zinc oxides in a proportion ofapproxi- Patented Feb. 28,- 1956 mately 2:1 to 5:1 by weight. The molybdenum disul-l. fide should be pure and the purified molybdenum vdi sulfide product, Molykote, of the AlphaC orpora'tion-is a suitable grade. A finelydivided molybdenum ,disul-g fide of powder fineness is' used. The leaded ziircoxide used in the composition may containbetween 5 and;

50% of commercial fumed lead oxide. The commercial fumed lead oxide is a basic lead sulfate having an empirical composition of approximately: ZPbOr-PbO.

The commercialbasic leadsulfate, which has a range of. 72-85%- PbSOe-and 15-28% PbO, issatisfactory. While; the commercial fumed leaded zinc oxide is entirely satis-. factory, other methods of preparing the zinc oxide and basic lead sulfate which. produce granules of finenessequivalent to that of the commercial fumed leadedwzinc; oxides are equally satisfactory. The co-fumed leaded zinc oxide or mixtures of separately prepared zinc oxide and basic lead oxide may be used. I

The'solid components are suspended in a drying vehicle. The drying vehicle may be of varnish, shellac, or, preferably, lacquer of the nitrocellulose type. While shellac and varnish are suitable from the standpoint of forming a uniform adherent dispersion of the solid components of the drawing compound, they are less satisfac tory than the lacquer in the point of drying time. The lacquer dries sufliciently rapidly that the coated metal may be drawn within about 5 minutes after application, whereas the shellac may require several hours and the varnish-base coating as much as 24 hours drying before drawing may be attempted. While the lacquer may be used without dilution, the drying time can be improved by the addition of a typical lacquer thinner such as ethyl, butyl, or amyl acetate, acetone, methyl ethyl ketone, cyclohexanone, glycol ethers, etc. The lacquer, even when thinned by as much as 3 parts of lacquer thinner per part of lacquer, retains sufiicient viscosity to adequately suspend the solids therein. ponent of the compound is important since it-wasfound that the solid components of the compound could not be used either alone or with othersuspending'agents to obtain satisfactory results.

The preparation and use of the wire drawing composition may be illustrated by the-following example.

Example about 35% basic lead sulfate consisting of about lead sulfate and 20% lead oxide. The mixture of molybdenum disulfide and leaded zinc oxide was then introduced into a medium consisting of 37.5 cc. of commercial lacquer thinner and 12.5 cc. of commercial nitrocellulose lacquer. The lubricant was used on test specimensof thorium rod. The specimens consisted of 1- foot lengths of thorium wire, 0.070 to 0.100 inch in diameter, which had been prepared from hot-rolled M4- inch diameter thorium rod by drawing the rod in a copper jacket. Each sample was pointed by swaging prior to the applicationof the lubricant and the rods were then drawn through a tungsten carbide type die .to effect a reduction ofapproximately 21%. It was found that with the above lubricant the thorium rods could be drawn without seizing or galling arid the surface of the drawn wire was smooth. Two, and in some cases three, passes of the rod through the die could he made-with one application of the lubricant. Two draws with one application of lubricant were desirable, since it was found that with one draw the resultant wire had a tendency to be slightly uneven in diameter. This is believed to result from an uneven coating of the lubricant. However, the first draw would leave a thin uniform coating The drying com-' The of the lubricant on the wire, while removing all excess lubricant, and a second pass through the die with the wire would then leave the wire even and smooth. It was found that the wire had to be completely covered with the lubricant, since any unlubricated spots would seize or gall to the die. Since the compound is a suspension, it was important that the mixture be well mixed before application to the rod.

It will be understood that this invention is not to be limited to the details given herein but that it may be modified within the scope of the appended claims.

What is claimed is:

1. A wire drawing composition consisting essentially .of a mixture of 2 to 5 parts by Weight molybdenum disulfide and 1 part by weight of finely divided leaded zinc oxide suspended in a drying vehicle.

2. The composition of claim 1 wherein the drying vehicle is a mixture of nitrocellulose lacquer and lacquer thinner.

3. The composition of claim 1 wherein the drying vehicle is shellac.

4. A composition of 2-5 "parts by weight molybdenum disulfide to 1 part by weight fumed lead-zinc oxides suspended in a drying medium consisting of 1 part nitrocellulose lacquer and 3 parts lacquer thinner.

References Cited in the file of this patent UNITED STATES PATENTS 2,085,512 Schneider June 29, 1937 2,085,528 Grenquist June 29, 1937 2,139,013 Grace Dec. 6, 1938 2,197,605 Barton Apr. 16, 1940 2,330,050 Hallouis et al. Sept. 21, 1943 2,361,211 Kalischer Oct. 24, 1944 2,421,543 Cook June 3, 1947 2,619,458 McBride Nov. 25, 1952 

1. A WIRE DRAWING COMPOSITION CONSISTING ESSENTIALLY OF A MIXTURE OF 2 TO 5 PARTS BY WEIGHT MOLYBDENUM DISULFIDE AND 1 PART BY WEIGHT OF FINELY DIVIDED LEADED ZINC OXIDE SUSPENDED IN A DRYING VEHICLE. 